1. Technical Field
The present invention relates to a round window driving vibrator, and more particularly to a two-magnet three-coil type round window driving vibrator, which is provided to an inlet of a round window in a cochlea to allow a person suffering from hearing loss to hear, and includes two permanent magnets arranged to have the same magnetic poles adjoining each other and three coils disposed around the permanent magnets such that a direction of electric current flowing through one of the coils is opposite to the direction of the electric current flowing through another coil adjacent thereto, in order to increase driving force without being affected by an external magnetic field.
2. Description of the Related Art
In many countries, as a low birth rate and increasing longevity lead to an expanding elderly population and the number of persons suffering from hearing loss increases due to frequent exposure to noise in daily life, demand for medical devices and otologic surgery for hearing aid tend to increase.
Hearing aids serve to amplify and modulate sound for a person suffering from hearing loss and can be classified based on the degree of difficulty in hearing and the placement position into an external type and an internal type. External type hearing aids can be conveniently mounted on the external ear, but has a disadvantage in that it cannot satisfy the needs for persons suffering from severe hearing loss.
Thus, internal type hearing aids are suited to persons suffering from severe hearing loss and can be classified into an implantable artificial middle ear for replacing the middle ear and an implantable artificial inner ear for replacing the inner ear.
The implantable artificial middle ear hearing aid generally includes a microphone and a vibrator, and has been mainly studied in that this type of hearing aid can achieve effective transfer of sound signals to persons suffering from severe hearing loss through a simple structure thereof. The human ear is composed of an external ear, a middle ear and an inner ear, and external sound signals are sequentially transferred therethrough. Most implantable artificial middle ear hearing aids are designed to apply vibration to the oval window of the cochlea through these paths of the ear. Recently, however, it has been spotlighted to develop implantable artificial middle ear hearing aids which apply vibration from the round window of the cochlea through a reverse path.
In the implantable artificial middle ear hearing aid, the vibrator may be classified into an electromagnetic vibrator including a permanent magnet and a coil, and a piezoelectric vibrator including a piezoelectric device and electrodes. In designing the vibrator of the implantable artificial middle ear hearing aid, various factors such as biostability, biocompatibility, a smaller volume for easier implantation, and low power consumption are taken into consideration. To this end, there is a need for high performance vibrators. Particularly, despite low design costs, the piezoelectric vibrator has difficulty in realizing a high voltage output unit for operation of the vibrator while minimizing power consumption under spatial restriction.
Although the electromagnetic vibrator is broadly used for compensating for hearing of a person suffering from sensorineural hearing loss, a round window driving vibration transducer employing the electromagnetic method provides low driving force, making it difficult to achieve improved efficiency, particularly, in a high frequency band.